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ISHS Acta Horticulturae 1144: III International Symposium on Postharvest Pathology: Using Science to Increase Food Availability

Ecological fitness of yeasts to control postharvest diseases of fruits and its impact on formulation and practical application

Authors:   M.H. Jijakli, R. Lahlali
Keywords:   yeast, ecological fitness, postharvest diseases of fruits, biological control
DOI:   10.17660/ActaHortic.2016.1144.8
Biocontrol of postharvest fruit decays may be reached by postharvest application of antagonists and preharvest spraying of biocontrol agents in the field. Preharvest treatment allows the antagonist to colonize the fruit surface and any wounds inflicted during harvest before the arrival of pathogens. Numerous studies have pointed out the real practical problem of promoting the effective establishment of prospective antagonists in a natural environment. This can be crucial, limiting the consistency of biocontrol under field conditions and the widespread commercialization of biocontrol agents. The fluctuation of abiotic factors such as temperature, relative humidity and UV radiation has impacted the biological proprieties of biocontrol agents. Results presented here demonstrate that both antagonistic Pichia anomala strains K and Canadida oleophila strain O are very sensitive relative humidity (RH) and sunlight. Low RH and the initial applied concentration greatly affected the final antagonistic density on apple fruit surface. Similarly, the growth of Penicillium expansum is limited at RH close to saturation. The use of skimmed milk (1%) in combination with strain O was effective in protecting it against low RH. In order to protect both strains against the adverse effect of sunlight, different UV-protectants were assayed. Lignin and folic acid reduced the mortality of strain K caused by UV-B radiations and increased significantly its ability to control in situ P. expansum while riboflavin and uric acid were the most effective in situ to protect the strain O against UV radiations. This work highlight the sensitivity of both antagonistic yeasts to environmental factors, suggesting the need of appropriate improved formulations to overcome environmental stress when applied preharvest.

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